1. Field of the Invention
The present invention relates to methods for manufacturing display devices that include light-emitting elements, such as electroluminescent (hereinafter referred to as EL) elements and LED (light emitting diode) elements, and to display devices manufactured in accordance with these methods.
2. Description of Related Art
In active matrix displays using current-controlled light-emitting elements, such as organic EL elements and LED elements, such light-emitting elements emit light by themselves. Therefore, unlike liquid crystal displays, these active matrix displays do not need any backlight, and provide advantages including visibility that is less dependent upon angle.
In these display devices, generally, a plurality of light-emitting elements are arrayed in a matrix. Adjacent light-emitting elements are separated by an insulative, light-shielding protrusion referred to as a bank layer.
In order to form the display devices, a liquid material for forming a hole injection layer, and a liquid material for forming an organic EL layer or an organic semiconductive layer, are discharged, by, for example, an ink-jet method, into compartments separated by bank layers, that is, into pixels, to deposit a hole injection layer and an organic EL layer or an organic semiconductive layer in the compartments. This protruding bank layer prevents the precursors for these layers from extending into adjacent compartments when the precursors are discharged.
In addition, this light-shielding bank layer prevents light from passing through gaps between pixels, and colors from being mixed with each other between the adjacent pixels, and thus increases the contrast ratio when a completed display device is operated.
On the other hand, boundary areas between the light-emitting elements have driving elements, such as thin-film transistors (hereinafter referred to as TFT), for driving the light-emitting elements and various wires connected to the driving elements. The wires are formed of, for example, aluminum or the like. In addition, these boundary areas are provided with a light-shielding layer for preventing the TFTs from generating an optical leakage current.
The present invention is directed to a method for manufacturing a display device that includes a light-transmitting substrate and, above the light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements connected to the light-emitting elements, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and wires connected to the driving elements. The method includes the steps of: forming the wires on the light-transmitting substrate by patterning a light-shielding, conductive layer so as to have a shape in plan view corresponding to the shape of the bank layer in plan view; forming the bank layer by self-aligning above the wires on the substrate by exposing the wires, acting as a mask, from the rear surface of the substrate; and forming the light-emitting elements in the areas surrounded by the bank layer.
The present invention is also directed to a method for manufacturing a display device that includes a light-transmitting substrate and, above the light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements connected to the light-emitting elements, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and a light-shielding layer to shield at least part of the driving elements from light. The method includes the steps of: forming the light-shielding layer on the light-transmitting substrate by patterning a shape in plan view corresponding to the shape of the bank layer in plan view; forming the bank layer by self-aligning above the light-shielding layer on the substrate by exposing the light-shielding layer, acting as a mask, from the rear surface of the substrate; and forming the light-emitting elements in the areas surrounded by the bank layer.
A display device according to the present invention includes, above a light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements, each being connected to the corresponding light-emitting element, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and wires formed of a light-shielding, conductive film connected to the driving elements. The wires above the substrate act as a mask while being subjected to light exposure from the rear surface of the substrate to form the bank layer above the wires by self-aligning.
A display device according to the present invention includes, above a light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements, each being connected to the corresponding light-emitting element, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and wires formed of a light-shielding, conductive film connected to the driving elements. At least part of the wires has a shape in plan view corresponding to the shape of the bank layer in plan view.
A display device according to the present invention includes, above a light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements, each being connected to the corresponding light-emitting element, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and a light-shielding layer to shield at least part of the driving elements from light. The light-shielding layer above the substrate acts as a mask while being subjected to light exposure from the rear surface of the substrate to form the bank layer above the light-shielding layer by self-aligning.
A display device according to the present invention includes, above a light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements, each being connected to the corresponding light-emitting element, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and a light-shielding layer to shield at least part of the driving elements from light. The light-shielding layer has a shape in plan view corresponding to the shape of the bank layer in plan view.
An electronic apparatus according to the present invention includes a display device described above.
Cost reduction in manufacturing and enhancement of image quality, which are typical requirements for display devices, are strongly desired in the display devices discussed above, as well as in other display devices.
In the related art manufacturing method discussed above, unfortunately, a dedicated photomask must be used to form a bank layer. The manufacturing cost, therefore, increases due to the formation of the bank layer.
In addition, using the dedicated photomask to form the bank layer of the display devices in the related art method reduces and varies the aperture ratio in pixels according to the alignment accuracy between the various light-shielding wires or the driving elements and the bank layer, which consequently makes it difficult to display bright and high-quality images.
Considering the above-described problems, the present invention provides a method for manufacturing a display device in which the manufacturing cost is reduced, and which ensures a high aperture ratio and a reduced variation of aperture ratios in pixels. The invention also provides a display device that is capable of displaying bright and high-quality images.
A first method for manufacturing a display device according to an embodiment of the present invention is a method for manufacturing a display device that includes a light-transmitting substrate and, above the light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements connected to the light-emitting elements, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and wires connected to the driving elements. The method includes the steps of: forming the wires on the light-transmitting substrate by patterning a light-shielding, conductive layer so as to have a shape in plan view according to the shape of the bank layer in plan view; forming the bank layer by self-aligning above the wires on the substrate by exposing the wires, acting as a mask, from the rear surface of the substrate; and forming the light-emitting elements in the areas surrounded by the bank layer.
According to the first method for manufacturing the display device, the wires are formed by patterning a light-shielding, conductive layer on the light-transmitting substrate so as to have a shape in plan view corresponding to the shape of the bank layer in plan view, in the step of forming the wires. Then, in the step of forming the bank layer, the light-shielding wires act as a mask while being exposed from the rear surface of the substrate to form the bank layer above the wires by self-aligning. Specifically, for example, a black resist is subjected to lithography and etching using the wires, acting as a mask, to form the bank layer by self-aligning. Therefore, no dedicated photomask is necessary to form the bank layer. Then, in the step of forming the light-emitting elements, the light-emitting elements are formed in the areas surrounded by the bank layer. The light-emitting elements, therefore, do not extend beyond the areas surrounded by the bank layer. Also, the wires and the bank layer of the completed display device can have substantially the same shape in plan view, and therefore, the aperture ratio in pixels is hardly reduced due to the alignment accuracy between the wires and the bank layer, as in the related art discussed above, and the variation of the aperture ratio in pixels is reduced. As a result, an active matrix-driving display device that is capable of displaying bright and high-quality images can be manufactured at a relatively low cost.
Exemplary light-emitting elements according to the present invention include organic EL elements and LEDs that include an organic EL layer or an organic semiconductive layer.
In order to prevent the light-emitting elements from overflowing, preferably, the bank layer can have a thickness of, for example, 1 xcexcm or more, and a thickness larger than that of the light-emitting elements, or the bank layer can be formed of a water-repellent material. Light-emitting elements formed on the areas where the driving elements have already been formed are not involved in displaying images and increase unwanted current. Instead of forming the light-emitting elements, therefore, forming the bank layer on the areas where the driving elements have been formed is advantageous.
In an embodiment of the first method for manufacturing the display device, the step of forming the driving elements in the boundary areas may further be performed between the steps of forming the wires and forming the bank layer.
According to this method, a display device that has driving elements, such as TFTs, deposited between the wires and the bank layer can be manufactured at a relatively low cost.
A second method for manufacturing a display device according to the present invention is a method for manufacturing a display device that includes a light-transmitting substrate and, above the light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements connected to the light-emitting elements, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and a light-shielding layer to shield at least part of the driving elements from light. The method includes the steps of: forming the light-shielding layer on the light-transmitting substrate by patterning a shape in plan view corresponding to the shape of the bank layer in plan view; forming the bank layer by self-aligning above the light-shielding layer on the substrate by exposing the light-shielding layer, acting as a mask, from the rear surface of the substrate; and forming the light-emitting elements in the areas surrounded by the bank layer.
According to the second method for manufacturing the display device, the light-shielding layer is formed by patterning a shape in plan view corresponding to the shape of the bank layer in plan view on the light-transmitting substrate, in the step of forming the light-shielding layer. Then, in the step of forming the bank layer, the light-shielding layer after patterning acts as a mask, while being exposed from the rear surface of the substrate to form the bank layer above the light-shielding layer by self-aligning. Specifically, for example, a black resist is subjected to lithography and etching using the light-shielding layer as a mask to form the bank layer by self-aligning. Therefore, no dedicated photomask is necessary to form the bank layer. Then, in the step of forming the light-emitting element layers, the light-emitting elements are formed in the areas surrounded by the bank layer. The light-emitting elements, therefore, do not extend beyond the areas surrounded by the bank layer. Also, the light-shielding layer and the bank layer of the completed display device can have substantially the same shape in plan view, and therefore, the aperture ratio in pixels is hardly reduced due to the alignment accuracy between the fight-shielding layer and the bank layer, as in the related art discussed above, and the variation of the aperture ratio in pixels is reduced. As a result, an active matrix-driving display device that is capable of displaying bright and high-quality images can be manufactured at a relatively low cost.
In an embodiment of the second method for manufacturing the display device, the step of forming the driving elements in the boundary areas may further be performed between the steps of forming the light-shielding layer and forming the bank layer.
According to this method, a display device that has elements, such as TFTs, deposited between the light-shielding layer and the bank layer, is manufactured at a relatively low cost.
In another embodiment of the second method for manufacturing the display device, the driving elements may include thin-film transistors. The light-shielding layer is patterned so as to cover at least channel regions of the thin-film transistors at the light-transmitting substrate side of the thin-film transistors in the step of forming the light-shielding layer.
According to this method, the display device has a structure in which the channel regions of the thin-film transistors are covered with the light-shielding layer from the upper side or the under side of the thin-film transistors, and the occurrence of optical leakage current in the thin-film transistors is reduced. Thus, a display device, in which the thin-film transistors having such excellent characteristics drive the light-emitting elements, can be manufactured at relatively low cost.
In another embodiment of the second method for manufacturing the display device, a conductive light-shielding layer serving as wires may be formed in the step of forming the light-shielding layer.
According to this method, a display device is provided which can relatively easily be manufactured, which has a light-shielding layer serving as wires in addition to its primary function, and which has a simple layered structure. For example, the light-shielding layer serving as wires set at a constant potential stabilizes the potential in the vicinity of the driving elements, and thus, the operation of the driving elements can be enhanced.
In another embodiment of the first or the second method for manufacturing the display device, the step of forming the light-emitting elements may include a sub step of using an ink-jet method to form at least part of the light-emitting elements.
By discharging, for example, a precursor which is a liquid material to form a hole injection layer, and further another precursor which is a liquid material to form an organic EL layer or an organic semiconductive layer, into compartments separated by the bank layer, by the ink-jet method, that is, into pixels, the hole injection layer and the organic EL layer or the organic semiconductive layer can be disposed in the compartments.
In another embodiment of the first or the second method for manufacturing the display device, the step of forming the light-emitting elements may include a sub step of forming an organic EL layer or an organic semiconductive layer.
According to this method, the display device having organic EL elements or LEDs can relatively easily be manufactured, while the bank layer is preventing the organic EL layer or the organic semiconductive layer from extending into the adjacent compartments.
A first display device according to the present invention includes, above a light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements, each being connected to the corresponding light-emitting element, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and wires formed of a light-shielding, conductive film connected to the driving elements. The wires above the substrate act as a mask, while being subjected to light exposure from the rear surface of the substrate to form the bank layer above the wires by self-aligning.
According to the first display device, the wires and the bank layer have substantially the same shape in plan view, and therefore, the aperture ratio in pixels is hardly reduced due to the alignment accuracy between the wires and the bank layer, as in the related art discussed above, and the variation of the aperture ratio in pixels is reduced. As a result, bright and high-quality images can be displayed.
A second display device according to the present invention includes, above a light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements, each being connected to the corresponding light-emitting element, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and wires formed of a light-shielding, conductive film connected to the driving elements. At least part of the wires has a shape in plan view corresponding to the shape of the bank layer in plan view.
In an embodiment of the first or the second display device, the wires may include at least one of data lines, scanning lines, capacitor lines, and common power lines.
According to this structure, the data lines, the scanning lines, the capacitor lines, or the common power lines make it possible to perform relatively complicated active matrix-driving. Also, providing a bank layer having substantially the same shape as the data lines, the scanning lines, the capacitor lines, or the common power lines in plan view makes it possible to display bright and high-quality images.
A third display device according to the present invention includes, above a light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving elements, each being connected to the corresponding light-emitting element, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and a light-shielding layer to shield at least part of the driving elements from light. The light-shielding layer above the substrate acts as a mask, while being subjected to light exposure from the rear surface of the substrate to form the bank layer above the light-shielding layer by self-aligning.
According to the third display device, the light-shielding layer and the bank layer have substantially the same shape in plan view, and therefore the aperture ratio in pixels is hardly reduced due to the alignment accuracy between the light-shielding layer and the bank layer, as in the related art discussed above, and the variation of the aperture ratio in pixels is reduced. As a result, bright and high-quality images can be displayed.
A fourth display device according to the present invention includes, above a light-transmitting substrate, a plurality of light-emitting elements arrayed in a plane, driving, elements, each being connected to the corresponding light-emitting element, a bank layer disposed in the boundary areas between the plurality of light-emitting elements, and a light-shielding layer to shield at least part of the driving elements from light. The light-shielding layer has a shape in plan view corresponding to the shape of the bank layer in plan view.
In an embodiment of the third or the fourth display device, the driving elements may include thin-film transistors. The light-shielding layer is patterned so as to cover at least channel regions of the thin-film transistors at the underside of the thin-film transistors.
According to this structure, at least the channel regions of the thin-film transistors are covered with the light-shielding layer from the underside of the thin-film transistors on the substrate, and thus, the occurrence of optical leakage current in the thin-film transistors is reduced. The light-emitting elements, therefore, can be driven by thin-film transistors having such excellent characteristics. As a result, high-quality images can be displayed.
In another embodiment of the third or the fourth display device, the driving elements may include thin-film transistors. The light-shielding layer is patterned so as to cover at least channel regions of the thin-film transistors at the upper side of the thin-film transistors.
According to this structure, at least the channel regions of the thin-film transistors are covered with the light-shielding layer at the upper side of the thin-film transistors on the substrate, and thus the occurrence of optical leakage current in the thin-film transistors is reduced. The light-emitting elements, therefore, can be driven by thin-film transistors having such excellent characteristics. As a result, higher-quality images can be displayed.
The light-shielding layer may be disposed at both upper and under sides of the thin-film transistors.
In another embodiment of any one of the first to fourth display devices, the light-emitting elements may include an organic EL layer or an organic semiconductive layer.
According to this structure, the bank layer prevents the organic EL layer or the organic semiconductive layer from extending into the adjacent compartments, and therefore the display device can display high-quality images using the reliable organic EL elements or LEDs.
In another embodiment of any one of the first to fourth display devices, the driving elements may include a plurality of thin-film transistors for each light-emitting element.
According to this structure, by combining, for example, two thin-film transistors, current-controlled light-emitting elements, such as organic EL elements, in pixels can be controlled.
Another embodiment of any one of the first to fourth display devices may further include a peripheral circuit connected to the driving elements or the wires in the peripheral region on the substrate. Part of the wire of the peripheral circuit is formed with the same layer as the wires or the light-shielding layer.
Thus, a so-called peripheral circuit-containing display device can be achieved which contains a peripheral circuit, such as a scanning line driving circuit and a data line driving circuit, having wires formed with the same layer as the wires or the light-shielding layer in the image-displaying section.
An apparatus according to the embodiment of the present invention includes any one of the first to the fourth display devices.
The above-described effects and other advantages of the present invention will become clear from the following description of the embodiments.